Britain's Lynsey Sharp says there is "nothing anyone can do" against dominant South Africa runner Caster Semenya in the 800m at the Olympics.
Semenya, 25, was subject to gender testing after winning gold at the 2009 World Championships in Berlin.
She has the fastest time of the year with two runs of one minute 56.64 seconds.
Sharp, fourth in the Birmingham Diamond League, said: "I can run faster but I can't control what other people do."
Semenya was cleared to compete in 2010 after being sidelined for 11 months while she had tests.
She won silver at the 2011 World Championships and 2012 Olympics, but having claimed gold in 1:55.45 six years earlier, she failed to qualify for last August's world final, finishing last in her semi-final in 2:03.18.
New regulations requiring female athletes to take testosterone-lowering medication if their levels were above the legal mark were suspended for two years by the Court of Arbitration for Sport last July.
Sharp, 25, ran 1:59.29 at Sunday's race in Birmingham race, which was won in 1:56.92 by Francine Niyonsaba of Burundi.
Asked about the Olympics in August, she added: "It's two races, so there's nothing I can do, there's nothing anyone else can do. It's out of our control."